AT&T has seen "extraordinary demand" for iPhone 4S with more than 200,000 preorders in the first 12 hours alone, the most successful iPhone launch the company ever had.

The iPhone 4S was unveiled on Tuesday and immediately underwhelmed fans who had hoped for a revolutionary design after a wait of more than 15 months.

However, Apple is betting that hardware updates (dual-core processor, 8mpx camera) and software enhancements (iOS 5), including a well-reviewed voice-recognition software system, will pull in buyers.

AT&T, Verizon Wireless and Sprint began taking U.S. online orders for the device on Friday.

The latest iPhone 4S hits store shelves around the world on October 14.

Sprint iPhone sales were not mentioned during a a news conference by Spring on Friday, in which the company outlined its 4G strategy.